Recently, with the social demand for energy saving, it is strongly desired for automobiles to reduce heat generation by rubber for tires and to reduce fuel consumption. Accordingly, as the rubber composition for use for treads and others of tires, desired is a rubber composition having a low tan δ (hereinafter this may be referred to as “low-loss property”) and excellent in low heat generation. Further, the rubber composition for treads is desired to be excellent in abrasion resistance, fracture characteristics and grip performance in addition to the-loss property thereof, from the viewpoint of safety and economic efficiency.
Against the problems, heretofore it is known that, when a terminal modifying group is introduced into a polybutadiene used in a rubber composition, then the modifying group may react with the filler in the composition to improve the affinity of the rubber component with the filler, whereby the amount of bound rubber increases and, as a result, the abrasion resistance of the rubber composition is thereby enhanced (for example, see Patent Reference 1).
However, the rubber composition of the time could attain sufficient abrasion resistance but involves some problems in that such an expensive modified polymer must be used and the workability of the composition worsens.